Pseudancistrus sidereus is described from two collections of specimens from Amazonas, Venezuela. Pseudancistrus sidereus differs from all other members of Pseudancistrus based on the presence of a unique keel on the caudal peduncle formed from the concave dorsal sections of the plates in the ventral series, light spots on the body (these may be yellow in life) centered on the body plates and the absence of the characteristics of the more derived members of Pseudancistrus such as hypertrophied odontodes along the snout in males and females and the loss of evertibility of the cheek plates. Pseudancistrus includes Lithoxancistrus and Guyanancistrus and is diagnosed by the following synapomorphies: no suture between pterotic-supracleithrum and hyomandibula, no contact of the hyomandibula with the prootic, straight, spoon-shaped anterior process of metapterygoid, nasal bone not much wider than laterosensory canal running through it, sphenotic not contacting posteriormost infraorbital externally, and a short ventral ridge on the pelvic basipterygium (lost in some species). Two species formerly assigned to Guyanancistrus are placed in different genera. Hypostomus guacharote is placed in Lasiancistrus and Chaetostomus trinitatis is placed in Ancistrus.Se describe Pseudancistrus sidereus, con base en dos colectas de espec menes del Amazonas venezolano. Pseudancistrus sidereus difiere de los otros miembros del g nero Pseudancistrus por la presencia de una quilla nica en el ped nculo caudal formada a partir de las secciones c ncavas dorsales de las placas de la serie ventral, puntos blancos en el cuerpo (probablemente amarillos en vida) centrados en las placas corporales y la ausencia de ciertas caracter sticas presentes en los miembros m s derivados de Pseudancistrus, como odontodos hiperatrofiados a lo largo del rostro en machos y hembras y la perdida de evertibilidad de las placas de la mejilla. Pseudancistrus incluye a Lithoxancistrus y Guyanancistrus y se diagnostica por las siguientes sinapomorf as: sutura entre el pter tico-supracleitro y la hiomand bula ausente, hiomand bula y pro tico sin contacto, proceso anterior del metapterigoides recto y en forma de cuchara, hueso nasal apenas m s amplio que el canal laterosensorial que corre a trav s del mismo, esfen tico sin contacto externo
Prevention of Fatal Pulmonary Thromboembolism by Heparin Prophylaxis after Surgery for Hip Fractures
